Expansion of a lithium gas in the BEC-BCS crossover
Résumé
We report on experiments in $^6$Li Fermi gases near Feshbach resonances. A broad $s$-wave resonance is used to form a Bose-Einstein condensate of weakly bound $^6$Li$_2$ molecules in a crossed optical trap. The measured molecule-molecule scattering length of $170^{+100}_{-60}$\,nm at 770\,G is found in good agreement with theory. The expansion energy of the cloud in the BEC-BCS crossover region is measured. Finally we discuss the properties of $p$-wave Feshbach resonances observed near 200\,Gauss and new $s$-wave resonances in the heteronuclear $^6$Li- $^7$Li mixture.